Belt terminology "A" vs "L"

[Stephen Tashiro]

The PDF https://www.regalpts.com/PowerTransmissionSolutions/Other/Belt%20Drive%20Monthly%27s/Form_9806E.pdf says a drive belt with a top width of 1/2" and depth of 5/16" could be named with an "A" or an "L". Are there other criteria that make an "A" and "L" different?

For example, the belt used by my evaporative cooler is named A56-4L-580.

[Tom M King]

https://blog.micrometl.com/hvac-the-basics-of-v-belts/